1. Field
The invention is in the field of exhaust systems for automobiles, and more specifically thin exhaust pipes for increased ground clearance on racing cars used on oval tracks such as stock cars.
2. State of the Art
Race cars used in automobile racing are typically constructed such that only a minimal amount of clearance is maintained between the underside of the car and the surface of the roadway or track. This is done to lower the center of gravity of the vehicle so as to improve vehicle handling and resistance to rolling over, and to minimize the drag on the car due to air passing thereunder. Likewise, such race cars typically have very stiff suspension systems which do not allow the vehicle to travel as great a distance up and down nor side-to-side as a standard production car allowing the use of less ground clearance. One of the problems encountered in lowering the race car closer to the race track is providing sufficient clearance for the vehicle exhaust system which is one of the lowest hanging components of a typical car, including race cars.
The problem is particularly acute on cars which race on oval race tracks such as stock cars. The exhaust pipes of such stock cars typically exit toward one or both sides of the car so as to minimize the length of the exhaust pipes and the resulting exhaust gas back pressure which back pressure lowers engine power output and overall engine performance. As such, the minimum ground clearance of the exhaust system typically occurs where the exhaust pipes cross under the longitudinally-extending main frame members of the chassis at the sides of the vehicle. Stock cars typically race on oval tracks in a counter-clockwise rotational direction with centrifugal force causing the body and chassis of the car to lean toward the outside of the turn or toward the right side of the car. Therefore, the ground clearance on the right side of the car is less during cornering and the greatest ground clearance results on the left side of the car during such cornering. Also, banked tracks can induce high downward loads to the suspension system of stock cars requiring additional ground clearance. In an effort to increase the ground clearance of the exhaust system on stock cars, thin profile boom tube exhaust pipes were developed which extend at a rearward, laterally outwardly-directed angle from the secondary exhaust pipes under the main frame members of the chassis. The outlet end of such boom tube exhaust pipe is typically manufactured in a squared-off or right angle end configuration and trimmed at installation to match exit angle and the side of the particular vehicle.
The construction of prior art boom tube exhaust pipes typically takes several forms. A first type of prior art boom tube includes a thin profile, generally flattened sheet metal body having a pair of spaced, parallel flat upper and lower sheet metal pieces and a pair of elongate, U-shaped cross-section sheet metal side pieces welded to respective side edges of the upper and lower sheet metal pieces so as to form a generally flattened tubular body. The upper and lower sheet metal pieces can be tapered so as to form a laterally tapered body which allows the exhaust gasses to expand while travelling therethrough. The upper and lower sheet metal pieces are typically interconnected by a plurality of short rods welded into staggered mating holes in such upper and lower sheet metal pieces. The rods are an attempt to minimize vibration of the broad upper and lower half shells which vibration can cause increased exhaust gas back pressure, resonance and increased noise, and metal fatigue. The boom tube exhaust pipe further includes a single funnel shaped inlet or a pair there of which is welded to one end of the generally flattened tubular body to connect with the secondary exhaust pipe or pipes of the vehicle. Such inlets typically comprise a longitudinally split thin walled metal tube, the respective halves of which are partially flattened, more so at one end than the other end, and each longitudinally welded at the edges thereof to a pair of upper and lower tapered flat plates, the narrower edge thereof being adjacent the less-flattened ends of the respective half tubes so as to form a generally funnel shaped inlet with a somewhat flattened circular inlet end and a generally flattened profile outlet end. Alternatively, such inlets can comprise a thin walled metal tube into the respective ends of which are forced appropriately shaped arbors or forms which stretch and form the tube into a somewhat flattened circular shaped inlet end and a generally flattened profile outlet end. Such boom tube exhaust pipe is expensive to manufacture due to the multitude of rods and welding involved and is still prone to metal fatigue due to the increased stresses in the half shells at the respective holes therethrough and due to the increased brittleness of the metal of the half shells and rods due to the heat applied during welding thereof.
A second type of prior art boom tube exhaust pipe comprises a large diameter, thin walled steel tube which is generally flattened so as to form a thin profile, generally flattened tubular body. The upper and lower portions of the tubular body can be interconnected by a plurality of rods as explained for the first version prior art boom tube exhaust pipe. A single funnel shaped inlet or a pair thereof of similar construction as that of the first version prior art boom tube is welded to one end of the flattened tubular body to connect with the secondary exhaust pipe or pipes of the vehicle. The tubular body of such boom tube exhaust pipe does not taper outwardly from the inlet end to the outlet end due to fabrication from a tube such that exhaust gasses cannot expand while moving therethrough, causing increased exhaust gas back pressure and suffers from the same disadvantages as the first version prior art boom tube exhaust pipe.
A third type of prior art boom tube takes the form of a rectangular extruded steel tube to which a pair of elongate U-shaped cross-section sheet metal side pieces are welded to the sides thereof to form a thin profile, generally flattened tubular body having three elongate passageways therein. A plurality of exhaust crossover holes are typically drilled or milled through the walls of the tube to allow crossover flow of exhaust gasses between the elongate passageways. A single funnel shaped inlet or a pair thereof of similar construction as that of the first version prior art boom tube is welded to one end of the flattened tubular body to connect the secondary exhaust pipe or pipes of the vehicle to direct the exhaust gasses into the ends of the respective tubes. A plurality of such rectangular tubes (or square tubes) can be welded together side-by-side in place of the single rectangular tube with the sheet metal side pieces welded to the two outermost tubes to form a thin profile, generally flattened tubular body of greater width than using a single rectangular tube. A plurality of exhaust crossover holes are typically drilled or milled through the walls of the tubes to allow crossover flow of exhaust gasses between the elongate passageways. A single funnel shaped inlet or a pair thereof is welded to one end of the flattened tubular body to connect the secondary exhaust pipe or pipes of the vehicle to direct the exhaust gasses into the ends of the respective tubes. While such boom tube exhaust pipe is more fatigue resistant than the sheet metal, the weight thereof is greater, the exhaust gas crossover tubes must typically be drilled or milled rather than less expensive punching thereof, and the body is not tapered such that exhaust gasses cannot expand while traveling therethrough resulting in increased exhaust gas back pressure.
Such prior art boom tube exhaust pipes can be constructed such that the inlet is at or above a lower plane of the body thereof so as to maximize ground clearance. Likewise, exhaust systems comprising a pair of headers each including a plurality of primary exhaust pipes which connect at one end thereof to the cylinder block of an internal combustion engine at respective exhaust outlet ports thereof and at opposite ends thereof which converge into a single merge collector, a pair of secondary exhaust pipes which connect to the outlet of the respective merge collectors, and one or two boom tube exhaust pipes are used in auto racing. Such exhaust systems can be made and mounted to a race car such that the entire exhaust system including the inlets of the boom tube exhaust pipes, are at or above the lower plane of the bodies of the boom tube exhaust pipes to maximize ground clearance of the exhaust system.
The invention firstly comprises a flattened profile exhaust pipe, or boom tube exhaust pipe for attachment to the end of a secondary exhaust pipe or exhaust pipe header assembly leading exhaust gasses away from the engine of a motor vehicle. The boom tube exhaust pipe mounts to the bottom portion of the frame or chassis of the motor vehicle typically adjacent the side of the vehicle and provides improved ground clearance between the exhaust pipe and the surface of the ground.
The boom tube exhaust pipe is of generally tubular configuration, comprising a tubular inlet having a first end of mating configuration for attachment to a secondary exhaust pipe or to an exhaust pipe header assembly, having an inlet opening for receiving exhaust gasses therefrom of generally circular or slightly flattened circular shape with the secondary exhaust pipe or exhaust pipe header assembly having a mating shape, the tubular inlet tapering from the first end to a second, thin profile, generally flattened end, and a tubular body of generally flattened shape corresponding to the second end of the tubular inlet, which tubular body extends therefrom and which terminates at an outlet opening for expelling the exhaust gasses into the atmosphere. As such, the bend radius of the respective side portions of the tubular inlet typically decreases uniformly from the first to second end thereof unlike prior art inlets. The flattened body can include a bottom surface lying generally in a plane with the bottom of the tubular inlet at or above the lower plane in a mounted position on the motor vehicle allowing all of the other pipes of the exhaust system lie at or above such plane so as to maximize ground clearance. The body can be flared laterally outwardly from the tubular inlet to the outlet opening so as to allow the exhaust gasses to expand while moving through the body yet without decreasing the ground clearance of the boom tube exhaust pipe. A structural rib can extend generally longitudinally through the body into the tubular inlet, which structural rib spans between and is affixed to the body juxtaposed an upper and a lower inside surface of the body, the portion within the inlet being tapered so as to also span between and is affixed to the inlet juxtaposed an upper and a lower inside surface of the tubular inlet so as to provide support to the tubular inlet and body. A plurality of holes can extend through the structural rib to allow exhaust gasses to flow between elongate passageways formed on each side thereof by the structural rib, the tubular inlet, and the body. The structural rib can comprise a web interconnecting respective upper and lower legs or flanges which extend laterally therefrom, such as in a C-shaped channel cross-section, which structural rib can be plug welded to the tubular inlet and the body through a plurality of holes such as round holes or slots through the tubular inlet and the body. The exhaust pipe can include a second tubular inlet of similar construction to the first laterally adjacent the first tubular inlet for attachment to a second secondary exhaust pipe. A second structural rib of similar configuration to the first structural rib can extend generally longitudinally through the body and into the second inlet which vertically spans between and is affixed to the inlet and the body juxtaposed an upper and a lower inside surface of the tubular inlet and the body like the first structural rib so as to provide support therebetween. A center spacer rib can extend generally longitudinally through the body generally laterally centered therein between the respective inlets and structural ribs. A pair of lateral spacer ribs can also be included which extend generally longitudinally through the body, each disposed laterally outside a respective structural rib. The spacer ribs provide further support to the body, reducing vibration and resulting fatigue failure of the metal of the body. On the dual inlet versions, laterally adjacent portions of the inlets can be vertically cut so as to mate or merge together laterally and be welded at the periphery therebetween to place the inlets closer together.
The invention further comprises boom tube exhaust pipes constructed from standard sheet metal which can be sheared, punched, and formed on standard hand operated punch presses and breaks or other comparable press to allow low cost, low volume production thereof as well as on high volume Computer Numerically Controlled (CNC) programmable punch presses and multiple station automated progressive stamping machines. The tubular inlet and body comprise a pair of sheet metal half shells which are welded together such as at respective peripheral seams. The half shells can comprise respective upper and lower half shells each of which can comprise inlet and body halves which are generally laterally welded together. The structural rib comprises a piece of sheet metal formed so as to have a longitudinally-extending web which interconnects respective laterally outwardly bent upper and lower legs or flanges which extend generally normally therefrom, such as forming a C-shaped channel cross-section. The portion of the structural rib which extends into the inlet is tapered so as to span between an upper and a lower inside surface of the inlet, such tapered portion being formed such as by splitting the upper and/or the lower leg or flange and forming at an angle relative to the remainder thereof. A plurality of punched holes can extend through the web of the structural rib to allow exhaust gasses to flow therethrough. The spacer ribs are constructed in a similar manner from sheet metal but without the tapered inlet portion. The structural ribs and spacer ribs can be plug welded to the half shells through a plurality of holes such as round holes or slots through the respective half shells. Single or dual inlet boom tube exhaust pipes can be made using such construction. On the dual inlet versions, laterally adjacent portions of the inlet halves of the upper and lower half shells can be vertically cut so as to mate or merge together laterally and be welded at the periphery between the inlet halves to place the inlets closer together.
The invention further comprises exhaust systems which include the boom tube exhaust pipes of the invention, such exhaust systems being for use on motor vehicles powered by an internal combustion engine having multiple power cylinders. Such exhaust systems comprise a pair of exhaust pipe header assemblies each of which include a plurality of primary exhaust pipes each connectable at a first end thereof to the engine block at a respective power cylinder exhaust port and a merge collector into which respective opposite ends of the primary exhaust pipes converge and are welded, a pair of transition pipes each having a first end connectable to one of the merge collectors and each having a second end, and a single boom tube exhaust pipe having a pair of inlets, or a pair of boom tube exhaust pipes each having a single inlet. The second ends of the transition pipes are connectable to the respective inlets of the single or dual inlet boom tube exhaust pipes. The single inlet version diverges to laterally opposite sides of the motor vehicle and the dual inlet version exits to one side of the motor vehicle.
The invention further comprises a method of construction of a boom tube exhaust pipe from standard sheet metal, comprising the steps of providing a pair of upper and lower half shells of formed sheet metal which include an inlet portion, a body portion, and an outer periphery, providing an elongate rib of formed sheet metal having a web which interconnects a pair of respective upper lower legs or flanges which extend laterally outwardly therefrom, placing the rib generally longitudinally within the half shells, welding the rib to the respective upper and lower half shells, and welding the outer peripheries of the half shells together. The method can be practiced wherein the welding of the rib to the respective upper and lower half shells is of the resistance spot welding type, or by using half shells each of which include a plurality of longitudinally extending plug weld holes such as round holes or slots punched therethrough and plug welding the rib to the respective upper and lower half shells through the plug weld holes. The half shells can comprise upper and lower half shells. Each of the upper and lower half shells can comprise separate inlet and body halves and the method further include welding the inlet and body halves of the respective upper and lower half shells together. The method can include construction of dual inlet boom tube exhaust pipes having a pair of structural ribs. The inlet halves of the upper and lower half shells can be made from separate pieces of sheet metal and can be vertically cut so as to mate or merge together laterally and the inner periphery between the inlets halves of the upper and lower half shells welded together. The method can include construction of a boom tube exhaust pipe having a center spacer rib and/or a pair of lateral spacer ribs each disposed laterally outside one of the respective structural ribs.
The single and dual inlet boom tube exhaust pipes of the invention, exhaust systems which include such exhaust pipes, and the methods of construction thereof can include boom tube exhaust pipes which are also acoustic mufflers, all of which this invention further comprises. In this regard, my previously issued U.S. Pat. No. 5,824,972 issued to me Oct. 20, 1998 titled xe2x80x9cAcoustic Mufflerxe2x80x9d is hereby incorporated by reference into this patent application. As such the tubular inlet or inlets and in particular the flattened tubular body of the boom tube exhaust pipe comprise the casing of the muffler and a plurality of spiral acoustic traps disposed therein provide the acoustic attenuation. The specific configurations of the combined boom tube exhaust pipe acoustic muffler include any of those disclosed in my prior xe2x80x9cAcoustic Mufflerxe2x80x9d patent, with a single longitudinally diagonally disposed row of acoustic traps being preferred in both the single and the dual inlet versions of the boom tube exhaust pipe acoustic muffler. In such configuration as well as in the other configurations thereof, any such structural ribs and/or spacer ribs can include longitudinal gaps between which the spiral acoustic traps can extend. Such boom tube exhaust pipe acoustic mufflers can also include metering screens, deflectors such as a V-shaped inlet deflector, and perforated metering plates, or any other such components disclosed in my prior xe2x80x9cAcoustic Mufflerxe2x80x9d patent. Such spiral acoustic traps can be affixed to the casing such as by fillet welding, plug welding, or resistance spot welding. The spiral acoustic traps can include one or more upper and lower locator tabs which are integral with or affixed to the spiral acoustic traps and which extend vertically upwardly and downwardly through corresponding generally rectangular or arcuate rectangular holes through the upper and lower walls of the casing or half shells. Such holes serve to locate and retain the spiral acoustic traps during assembly. Such tabs can be bent over upon assembly and are affixed to the casing such as by welding. Alternatively, such tabs can comprise bent ninety degree bent tabs integral with or separate pieces affixed to the spiral acoustic traps, which bent tabs fit juxtaposed the upper and lower surfaces of the casing, which tabs can be welded in a similar manner to the structural ribs, spacer ribs, and spiral acoustic traps. Such locating tabs and corresponding holes in the casing or half shells, and bent tabs can likewise be used on the metering screens, deflectors, perforated metering plates, and on any other such components used in the construction of the boom tube exhaust pipe acoustic muffler.
The boom tube exhaust pipe acoustic muffler can include a plurality of flat, curved, V-shaped, or otherwise bent baffle plates which route the exhaust gasses in a circuitous route therethrough so as to provide acoustic attenuation so as to lower the level of noise from the motor vehicle. Examples of such baffle arrangements in single and dual inlet versions include laterally extending, longitudinally spaced flat baffle plates which alternately extend from opposite sides of the casing with respective gaps between the free ends thereof and the opposite side portion of the casing for exhaust gasses to pass thereby so as to route the exhaust gases side-to-side in a generally horizontal plane. Such baffle plates can comprise laterally extending ribs of similar construction to the structural ribs and spacer ribs disclosed herein. The ends of the respective ribs which contact the side portions of the casing can be arcuate so as to match closely thereto without significant exhaust gas leakage therebetween. A second example of such baffle arrangement comprises a longitudinally extending series of alternating generally laterally disposed V-shaped plates and pairs of flat plates, the V-shaped plates disposed generally along the longitudinal centerline of the casing pointing toward the tubular inlet with gaps between the respective ends thereof and the side portions of the casing to allow exhaust gasses to pass thereby. The flat plates extend from respective side portions of the casing in a generally coplanar fashion, with a gap between the free ends thereof at the longitudinal centerline of the casing to allow exhaust gasses to pass thereby. As such, the exhaust gasses are generally split into two streams which pass by opposite ends of each V-shaped baffle plate and remix in the gap between the flat plates.
Other such examples of such arrangements of baffle plates include such as for the dual inlet version a pair of such above examples, comprising two complete sets of baffle plates as described in the previous examples, one generally centered about the longitudinal centerline of each of the respective inlets, the innermost plates of which can terminate at the center spacer rib rather than the side portion of casing or simply terminate such that exhaust gasses can pass therearound.
The best mode presently contemplated for carrying out the invention is illustrated in the accompanying drawings, in which:
FIG. 1 is a right front perspective view of a first embodiment of the exhaust pipe of the invention which has a single inlet pipe and two elongate passageways;
FIG. 2, a front elevational view taken on the line 2xe2x80x942 of FIG. 1 showing the relative cross-sections of the exhaust pipe;
FIG. 3, a rear elevational view taken on the line 3xe2x80x943 of FIG. 1 showing the relative cross-sections of the exhaust pipe;
FIG. 4, a longitudinal vertical sectional view taken on the line 4xe2x80x944 of FIG. 1 showing a first version exhaust gas cross-over holes in the support rib;
FIG. 5, a right front perspective view of a second embodiment of the exhaust pipe of the invention which has dual inlet pipes and four elongate passageways;
FIG. 6, a front elevational view taken on the line 6xe2x80x946 of FIG. 5 showing the relative cross-sections of the exhaust pipe;
FIG. 7, a rear elevational view taken on the line 7xe2x80x947 of FIG. 5 showing the relative cross-sections of the exhaust pipe;
FIG. 8, a longitudinal vertical sectional view taken on the line 8xe2x80x948 of FIG. 5 showing such first version exhaust gas cross-over holes in the right hand support rib;
FIG. 9, a longitudinal vertical sectional view taken on the line 9xe2x80x949 of FIG. 5 showing such first version exhaust gas cross-over holes in the spacer rib;
FIG. 10, a right front perspective view of a third embodiment of the exhaust pipe of the invention which has dual inlet pipes and six elongate passageways;
FIG. 11, a front elevational view taken on the line 11xe2x80x9411 of FIG. 10 showing the relative cross-sections of the exhaust pipe;
FIG. 12, a rear elevational view taken on the line 12xe2x80x9412 of FIG. 10 showing the relative cross-sections of the exhaust pipe;
FIG. 13, a longitudinal vertical sectional view taken on the line 13xe2x80x9413 of FIG. 10 showing such first version exhaust gas cross-over holes in the right hand support rib;
FIG. 14, a longitudinal vertical sectional view taken on the line 14xe2x80x9414 of FIG. 10 showing such first version exhaust gas cross-over holes in the spacer rib;
FIG. 15, a fragmentary longitudinal vertical sectional view of a rib showing a second version exhaust gas cross-over hole;
FIG. 15A, a fragmentary longitudinal vertical sectional view of a rib showing a third version exhaust gas cross-over hole, with the preferred direction of exhaust gas flow indicated by the arrows;
FIG. 15B, a fragmentary longitudinal vertical sectional view of a rib showing a fourth version exhaust gas cross over hole, with the preferred direction of exhaust gas flow indicated by the arrows;
FIG. 16, side elevational view of a race car having an eight cylinder engine and which has a single third embodiment exhaust pipe mounted thereto;
FIG. 17, a bottom plan view taken on the line 17xe2x80x9417 of FIG. 16 showing the primary exhaust pipes connecting to such third embodiment exhaust pipe, the mounting thereof to the chassis of the car, and with the portion thereof which is trimmed off to fit the exterior of the car indicated by phantom lines;
FIG. 18, a fragmentary lateral vertical sectional view taken on the line 18xe2x80x9418 of FIG. 17, rotated ninety degrees counter-clockwise, showing the details of the typical mounting of the exhaust pipe to the chassis of the car;
FIG. 19, a fragmentary bottom plan view of such race car having an eight cylinder engine and which has a pair of such first embodiment exhaust pipes mounted thereto, showing the primary exhaust pipes connecting to such first embodiment exhaust pipes, the mounting thereof to the chassis of the car, and with the portion of each thereof which is trimmed off to fit the exterior of the car indicated by phantom lines; and
FIG. 20, a fragmentary bottom plan view of a race car having a six cylinder engine and which has a pair such of first embodiment exhaust pipes mounted thereto, showing the primary exhaust pipes connecting to such first embodiment exhaust pipes, the mounting thereof to the chassis of the car, and with the portion of each thereof which is trimmed off to fit the exterior of the car indicated by phantom lines.